1. Field of Invention
This invention pertains to the art of methods and apparatuses for use in controlling the ground speed of a lawn mowing apparatuses, and more specifically to methods and apparatuses for use in controlling the ground speed of a walk-behind mower.
2. Description of the Related Art
It is well known to provide lawn mowing apparatuses, specifically lawn and garden lawn mowing apparatuses such as walk-behind lawn mowers, with apparatuses and methods for controlling their ground speed. One known method uses a spring loaded variable pitch pulley assembly attached to a rotating shaft. The variable pitch pulley assembly typically has two pulley halves forming a xe2x80x9cVxe2x80x9d shape for a belt connecting the pulley assembly to some type of transmission which is operatively connected to a drive axle. The belt tension is adjusted by any of various means known in the art. When the belt tension is increased, the two pulley halves are forced apart by the belt, allowing the belt to move inwardly toward the shaft. This movement decreases the effective belt diameter of the pulley assembly, supplying a slower speed to the transmission. When the belt tension is decreased, the spring causes the two pulley halves to move closer together, forcing the belt to move outwardly from the shaft. This movement increases the effective belt diameter of the pulley assembly, supplying a faster speed to the transmission.
Another known type is described in U.S. Pat. No. 4,117,652 to Jones et al. Jones et al. discloses a belt-driven transmission that is mounted on a deck of a mower between a pair of wheels. The transmission is driven through a pulley on the engine drive shaft and a pulley on the transmission connected by a belt. The pulley on the transmission includes an upper stationary half affixed to a splined end of a transmission input shaft and a lower half mounted for axial movement on the input shaft. A speed change lever is rotated about the input shaft and includes numerous sloping cam surfaces.
The present invention provides methods and apparatuses for controlling the ground speed of a lawn mowing apparatus using a non-spring loaded variable pitch pulley assembly and a control arm assembly. It is not necessary to adjust the belt tension because the control arm assembly is in contact with one of the pulley halves and it is used to adjust the distance between the two pulley halves. The variable pitch pulley is positioned between the motor and the cutting blade on the primary drive shaft. Thus, unlike Jones et al., the gear (pulley) ratios permit a maximum speed to be provided to the transmission. Also unlike Jones et al., a control arm adjusts the variable pitch pulley assembly using vertical adjustment along the length of the drive shaft. This is considered a significant improvement over the sloping cam surfaces provided by Jones et al.
In accordance with one aspect of the invention there is provided a variable speed mechanism for propelling an associated lawn mowing apparatus which has a body, a transmission which is operatively connected to a drive axle, a shaft, and means for rotating the shaft. The variable speed mechanism has a variable pitch pulley assembly with two pulley halves which is operatively connected to the shaft, a belt connecting the variable pitch pulley assembly to the transmission, a control arm assembly for controlling the distance between the two pulley halves, and means for selectively adjusting the control arm assembly. When the control arm assembly is adjusted, the distance between the two pulley halves is also adjusted. When the pulley halves are brought closer together the belt is force outwardly, away from the shaft, increasing the effective belt diameter of the pulley assembly. Thus, the belt supplies a faster speed to the transmission. When the pulley halves are brought farther apart, the belt under normal operating tension, is forced inwardly, toward the shaft, decreasing the effective belt diameter of the pulley. In this case, the belt supplies a slower speed to the transmission.
In accordance with another aspect of the present invention, there is provided a control arm assembly for use with a variable speed mechanism. The control arm assembly includes a control arm, a pivot shaft, a pivot bracket and a torsion spring. When the control arm is moved, it pivots around the pivot shaft and adjusts the distance between two pulley halves of a variable pitch pulley assembly.
In accordance with another aspect of the present invention, there provided a method for selectively controlling the speed of a lawn mowing apparatus. A speed selector positioned corresponding to the desired lawn mowing apparatus speed. Then tension is applied to a cable which moves the end of a control arm. The control arm adjusts the distance between two pulley halves. As the distance between the two pulley halves changes, so does the effective belt diameter. Once the effective belt diameter has been changed, the speed supplied by the belt to a transmission is correspondingly changed.
The benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.